Dental bonding agents are used to form a permanent bond between alloys of high-grade or low-grade metals or ceramics on one hand, and dental plastics on the other. The problem of improving the bond between plastics and dental prosthetic parts made of metal or ceramics is hardly new. Most recently, endeavors have intensified to achieve long-life composites.
As an example, U.S. Pat. No. 4,364,731 discloses a process in which a metal surface is coated by a magnetron sputterer in vacuum with an inorganic layer of silicon dioxide which is separated from the substrate by highly pure quartz glass. A similar method is described in German patent document DE-Cl 34 03 894 wherein the SiO.sub.x C layer is deposited by flame pyrolysis on the metal. However, these recent developments involve substantial equipment.
Another approach to improving the bonding between metal and plastic was based on the insight that additions of acrylic or methacrylic acid to monomers with radical polymerizing double bonds provide excellent adhesion. However, the drawback is incurred that the good bond of such metal-plastic composites is lost before very long due to humidity.